The three epidemics of ROP: A growing public health problem

The first ROP epidemic occurred in high-income countries in the 1940s and 1950s. It was associated with the improving survival rates of moderately preterm babies (32 to <37 weeks gestational age) with very low birth weights (<1,500 grams) who were being given unrestricted oxygen supplementation.

In the second ROP epidemic in the 1970s, the dominant feature was the extreme prematurity (< 28 weeks gestational age) of the affected babies. However, reported rates of ROP varied widely between different neonatal intensive care units (NICUs) including in high-income settings and after adjusting for case mix. This can be explained by differences in the quality of care being provided to preterm babies at the time, such as the variety of approaches taken to achieving and monitoring oxygen saturation targets.

In the early 1990s, an emerging third epidemic of ROP related blindness in children in low- and middle-income countries was initially detected by examining children in schools for the blind. This data was combined with global estimates of the prevalence of blindness to roughly calculate a global magnitude of ROP blindness of at least 50,000 children aged <15 years who were blind from ROP, with the highest proportion and numbers being in Latin America. In the late 90s, the risk of blindness from ROP in different regions and countries was predicted by plotting the proportion of blindness due to ROP against infant mortality rates. This showed that babies who develop ROP in low- and middle-income countries had a far wider range of birth weights and gestational ages than was the case in the UK, Canada or the USA.

Worryingly, the evidence suggests that this trend continues today. More accurate estimates have been derived from a 2010 systematic analysis of regional data which assessed:

• The prevalence of preterm birth amongst live births
• The number of preterm babies who received neonatal intensive care and survived
• The number of these survivors who were estimated to have developed ROP, and
• Those who were then affected by visual impairment.

The study found that, globally, 16% of preterm survivors (>184,700 babies) born at <32 weeks gestational age are estimated to have some degree of ROP, with 3% (32,300) developing associated visual impairment or blindness. The results also highlighted large regional differences in the distribution and severity of ROP.

Reasons for the third, ongoing epidemic of ROP blindness

• Rates of preterm birth are often higher in middle income countries than in high income countries
• A high proportion of women are delivered in health care facilities in middle income countries and premature babies are, therefore, likely to be admitted to neonatal intensive care
• Rates of severe ROP are higher in preterm babies in low- and middle-income countries which suggests that they are being exposed to risk factors which are now largely controlled in high income countries.

The evidence indicates that ROP is a growing global public health problem and that a wide range of programmatic control measures are needed from before birth to detect and treat ROP in preterm babies.

Watch the video to learn more about the epidemiology of ROP – its magnitude, distribution, determinants (causes) and how it is controlled – and understand the global ROP data trends and future projections.

What ROP data is kept in your setting? How is it used to guide the control of ROP?